U.S. Pat. No. 333,203 (1885) to Dick discloses an easel supported by an attached envelope.
U.S. Pat. No. 740,228 (1903) to Carpenter describes a message card adopted to fit on the handle of a door knob to be supported by the door.
U.S. Pat. No. 2,115,448 teaches an easel display support comprising two hinged flanges, means for maintaining an angle between the flanges, hinged struts for the flanges, and the flanges coated with a pressure sensitive adhesive.
U.S. Pat. No. 2,670,916 to Ranseen discloses a card supporting device having a back panel, retaining means for keeping it upright, a smaller front panel, means for securing the front panel to the back panel, and means for securing part of the front panel to the back panel while the unsecured part of the front panel provides gripping surfaces to grip and support a display card.
U.S. Pat. No. 2,919,512 to McDonald teaches an easel for holding cards or photographs comprising a holding body of transparent sheet material whose opposite edges are folded over to form slideway flanges, a prop insert having a joined prop tongue for sliding in the flanges, and the holder body constructed to receive the bottom of the prop insert.
U.S. Pat. No. 3,242,603 to Righenzi discloses a publicity card for display comprising a first sheet for receiving printing on its outer surface, flexible edges for the first sheet in order to form interned flaps, a second sheet hermetically sealed to the flaps of the first sheet to form a vented chamber as an air cushion between the sheets, an air vent in the second sheet, and hang-lip with a suspension hole in the edges of the second sheet overlaying the flaps.
U.S. Pat. No. 4,024,661 teaches a self-standing or telephone-mounted calendar comprising a sheet having a disc-shaped calendar, means for fixing the calendar to the central part of the dial of a telephone and a peripheral part positioned radially outward from the calendar, two cut lines nearly surrounding the calendar to separate it form the peripheral part, two connecting points to connect the peripheral part to the calendar part, the upper portion of the peripheral part being bendable backward to support the device, and an aperture to view the telephone number.